Q20 - Martha's friend, who is very

[karenlinn18]

Missed this one about flowers...ruled out answer C because of the "Some of" vs the "no" in the stimulus

[ManhattanPrepLSAT2]

This is a "match the flaw" q, and the key to your success is your ability to see the flaw in the original argument clearly.

Here's an analogous one that illustrates the issue.

Phil says there are no levi jeans that are waterproof.

However, there are levi jeans that are blue, and some blue things are waterproof.

Therefore, Phil must be wrong.

What is the flaw, specifically, in the argument? Assuming that because some (some just meaning an unknown number) jeans fit into a larger category (being blue) and some waterproof things that fit into a larger category of being blue, that there must be an overlap between these two groups (some jeans have to be waterproof). We know that is incorrect reasoning.

(C) is the only answer that mistakenly assumes that since two groups (sisters / poor students) are both a part of a larger group (on debate team) there must be an overlap between sisters and poor students.

Hope that helps!

[clarafok]

i see why C is right, but why is D wrong?

doesn't it also assume that two groups are both part of a larger group?

this is how i saw it:
sisters on debate team = friends are good swimmers
some on debate team are poor students = good swimmers are quite strong
at least 1 of sisters must be poor student = at least some of L's friends are quite strong

please help!

thanks in advance!

[ManhattanPrepLSAT2]

(D) is tempting here, but notice that in (D) there is a direct link between good swimmers and being quite strong -- when the LSAT, in an argument like this, says "are," that means every one of the elements in one category are in another. Therefore, according to (D), all people who are good swimmers are quite strong. Let's think about (D) in this terms:

Most of Leon's friends are good swimmers.

All good swimmers are quite strong.

So, likely that at least some of Leon's friends are quite strong.

Notice that, on this terms, (D) doesn't have the same flaw. In fact, you could argue (D) doesn't have a flaw at all. Hope that helps!

[clarafok]

i get it!

thanks!

[jwms]

The way I reasoned this question, and it may be quite sloppy, is as follows:

Some daisies are a kind of chrysanthemum
Some chrysanthemums are edible and palatable
Thus,
Some daisies are edible and palatable.

So it's a connection of Somes -- which can't work.

(C) says:

Some sisters are on the debate team
Some member of the debate team are poor students
Thus,
Some sisters are poor students.

Again -- connection of Somes.


(D) says:

Most of Leon's friends are good swimmers
All good swimmers are quite strong
Thus,
Some of Leon's friends are quite strong.

That can't be the match. It's a Most, All, and Some chain.


If this is an incorrect approach to this question, do let me know. Thank you.

[douglas.stratton]

I saw this as a 1+1 =/ 3 flaw. Adding up two things does not equal a third inference. I did miss the question between A and C because I was in a rush but I reviewed and it still helped to answer in this manner. Was this an illogical application of flaw?

[Sung MinP119]

why is (a) incorrect?